Hair dryer

ABSTRACT

A hair dryer has a casing, a switch, a blower, a mounting cylinder and multiple heating coils. The casing is hollow and has at least one air inlet and an air outlet. The switch is mounted on the casing. The blower is mounted in the casing and connects to the switch. The mounting cylinder is heat-resistant and insulating and is mounted in the casing. The heating coils are mounted around the mounting cylinder, are arranged abreast without any overlapping or interleaved parts and connect to the switch. At least one of the heating coils is wrapped in a clockwise direction and remains of the heating coils are wrapped in a counterclockwise direction. When the hair dryer turns on, the heating coils are electrified and currents on the heating coils are in a same direction to generate opposite magnetic forces canceling out each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hair dryer, and more particularly to a hand-held hair dryer that efficiently reduces the emission of the electromagnetic radiation deriving from the heating coils when operating and is safe for use.

2. Description of Related Art

Hair dryers are used widely nowadays. A typical hair dryer has a casing with an air outlet, a blower and a heating coil. When operating, the blower blows and causes airflow to pass through the electrified heating coil. The airflow is heated by the heating coil and then passes through the air outlet to blow a user's hair.

However, the spiral heating coil emits electromagnetic radiation that is harmful to human health when electrified.

An improved hair dryer disclosed in U.S. Pat. No. 6,891,102 B2, has a double wound heating coil with a reference number 40 in the specification to reduce the emission of the electromagnetic radiation. With reference to FIG. 4 of the '102 patent, the double wound heating coil has a first set of convolutions with a reference number 42 and a second set of convolutions with a reference number 44. The convolutions of the first set integrally form a first spiral coil section wrapped in a first direction. The convolutions of the second set are interleaved with the convolutions of the first set, and integrally form a second coil section connecting to the first coil section and wrapped back in a second direction opposite to the first direction. When the double wound heating coil is electrified, the electromagnetic radiation deriving from the first coil section cancel out the electromagnetic radiation deriving from the section coil due to the coil sections are wrapped in the opposite directions.

However, the double wound heating coil has several defects as follows:

1. The typical heating coil is mounted in the casing by wrapping the heating coil around a mounting cylinder mounted securely in the casing. The double wound heating coil can be wrapped hardly around the mounting cylinder due to the coil sections wrapped in the opposite directions.

2. Even though the double wound heating coil is mounted to the mounting cylinder by extending fasteners such as rivets through the double heating coil and the mounting cylinder, the fabrication of the hair dryer becomes complicated and therefore the cost of the hair dryer is increased.

3. A short circuit occurs and therefore to generate excessive heat and break the hair dryer when the double wound coil with the interleaved convolutions deforms and breaks.

To overcome the shortcomings, the present invention provides a hair dryer to mitigate or obviate the aforementioned problems.

SUMMARY OF THE INVENTION

The main objective of the invention is to provide a hand-held hair dryer that efficiently reduces the emission of the electromagnetic radiation deriving from the heating coils when operating and is safe for use.

A hair dryer in accordance with the present invention comprises a casing, a switch, a blower, a mounting cylinder and multiple heating coils. The casing is hollow and has at least one air inlet and an air outlet. The switch is mounted on the casing. The blower is mounted in the casing and connects to the switch. The mounting cylinder is heat-resistant and insulating and is mounted in the casing. The heating coils are mounted around the mounting cylinder, are arranged abreast and kept free from overlapping and interleaved parts and connect to the switch. At least one of the heating coils is wrapped in a clockwise direction and at least one of the heating coils is wrapped in a counterclockwise direction. When the hair dryer turns on, the heating coils are electrified and currents on the heating coils are in a same direction to generate opposite magnetic forces canceling out each other.

Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view in partial section of a hair dryer in accordance with the present invention;

FIG. 2 is an enlarged side view of a first embodiment of a hair dryer with the heating coils generating maximum heat, wherein horizontal arrows illustrate the magnetic forces along the axes of the heating coils and vertical and curved arrows illustrate the current;

FIG. 3 is an enlarged side view of the hair dryer in FIG. 2 with one heating coil generating average heat;

FIG. 4 is an enlarged side view of the hair dryer in FIG. 2 with the heating coils generating minimum heat;

FIG. 5 is an enlarged side view of a second embodiment of a hair dryer with the heating coils generating maximum heat, wherein horizontal arrows illustrate the magnetic forces along the axes of the heating coils and vertical and curved arrows illustrate the current;

FIG. 6 is an enlarged side view of the hair dryer in FIG. 5 with one heating coil generating average heat;

FIG. 7 is an enlarged side view of the hair dryer in FIG. 5 with the heating coils generating minimum heat; and

FIG. 8 is an enlarged side view of a third embodiment of a hair dryer in accordance with the present invention with the heating coils generating heat, wherein horizontal arrows illustrate the magnetic forces along the axes of the heating coils and vertical and curved arrows illustrate the current.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 1, a hair dryer in accordance with the present invention comprises a casing (10), a switch (20), a blower, a mounting cylinder (50) and multiple heating coils.

The casing (10) is hollow and has a handgrip, a barrel (12), a cavity, at least one air inlet (11) and an air outlet (13). The handgrip is formed on the casing (10). The barrel (12) is formed on the casing (10) and has a passage defined in the barrel (12). The cavity is defined in the casing (10) and communicates with the passage. The at least one air inlet (11) and the air outlet (13) are defined in the casing (10) and communicate with the cavity.

The switch (20) is mounted on the handgrip and may selectively slide between multiple positions to vary the temperature of the airflow generated by the hair dryer.

The blower is mounted in the cavity in the casing (10) and has a motor (30) and a fan (40). The motor (30) is mounted in the cavity in the casing (10) and connects to the switch (20), so the motor can be turned on or off through the switch (20). The fan (40) is connected rotatably to and driven by the motor (30) and is adjacent to the at least one air inlet (11).

The mounting cylinder (50) is heat-resistant and insulating, is mounted securely in the passage in the barrel (12) and has an inside end adjacent to the at least one air inlet (11) and an outside end adjacent to the air outlet (13).

The heating coils are wrapped spirally around the mounting cylinder (50), are arranged abreast without any overlapping or interleaved parts and connect to the switch (20).

At least one of the heating coils may be wrapped in a clockwise direction and remains of the heating coils may be wrapped in a counterclockwise direction. When the hair dryer is turned on, the heating coils are electrified and currents on the heating coils are in a same direction to generate opposite magnetic forces canceling out each other.

Alternatively, all of the heating coils may be wrapped spirally around the mounting cylinder (50) in a clockwise direction. When the hair dryer is turned on, the heating coils are electrified and a current on at least one of the heating coils is in a first direction such as from the outside end to the inside end of the mounting cylinder (50). The currents on remains of the heating coils are in a second direction such as from the inside end to the outside end opposite to the first direction. Therefore, opposite magnetic forces are generated and cancel out each other.

Alternatively, each heating coil may have a first coil segment wrapped in a clockwise direction and a second coil segment formed integrally with the first coil segment and wrapped in a counterclockwise direction. When the hair dryer is turned on, the heating coils are electrified and the first and second coil segments of each heating coil generate opposite magnetic forces canceling out each other.

With reference to FIGS. 2 to 4, a first embodiment of the hair dryer in accordance with the present invention has a first heating coil (60A), a second heating coil (60B) and a third heating coil (60C). The first heating coil (60A) is wrapped spirally around the mounting cylinder (50) in a clockwise direction and has two contacts (A1, A2). The second heating coil (60B) is wrapped spirally around the mounting cylinder (50) in a counterclockwise direction and has two contacts (B1, B2). The third heating coil (60C) is wrapped spirally around the mounting cylinder (50) in the counterclockwise direction and has two contacts (C1, C2).

The heating coils (60A, 60B, 60C) may be connected and electrified in different ways by adjusting the switch (20) to change the extent to which the heating coils (60A, 60B, 60C) totally heat.

When the switch (20) is adjusted to make the heating coils (60A, 60B, 60C) generate a maximum heat, the second and third heating coils (60B, 60C) connect to each other in parallel and then connect to the first heating coil (60A) in series. The contacts (B2, C1) connect to each other. A first current from a power source flows into the contact (A1) and flows out of the contact (A2). A second current in a same direction with the first current flows into the contact (B1) and flows out of the contact (C2), as shown in FIG. 2. According to the right hand rule for Ampere's law, the electrified first heating coil (60A) generates a magnetic force in a first direction along an axis of the mounting cylinder (50) and the electrified second and third heating coils (60B, 60C) generate a magnetic force in a second direction opposite to the first direction. The opposite magnetic forces cancel out each other and therefore to reduce the electromagnetic radiation of the hair dryer.

When the switch (20) is adjusted to make the heating coils (60A, 60B, 60C) generate an average heat, the first heating coil (60A) is not electrified. The second and third heating coils (60B, 60C) connect to each other in series. The contacts (B2, C2) connect to each other. A current from the power source flows into the contact (B1) and flows out of the contact (C1), as shown in FIG. 3. The current on the second heating coil (60B) from the outside end to the inside end of the mounting cylinder (50) is opposite to the current on the third heating coil (60C) from the inside end to the outside end. Therefore, the second and third electrified heating coils (60B, 60C) generate opposite magnetic forces canceling out each other to reduce the electromagnetic radiation of the hair dryer.

When the switch (20) is adjusted to make the heating coils (60A, 60B, 60C) generate a minimum heat, the heating coils (60A, 60B, 60C) connect to each other in series. The contacts (A2, B1) connect to each other. The contacts (B2, C1) connect to each other. A current flows into the contact (A1) and flows out of the contact (C2), as shown in FIG. 4. A magnetic force from the electrified first heating coil (60A) opposes and cancels out a magnetic force from the electrified second and third heating coils (60B, 60C) and therefore the electromagnetic radiation of the hair dryer is reduced.

With reference to FIGS. 5 to 7, a second embodiment of the hair dryer in accordance with the present invention has a first heating coil (60D), a second heating coil (60E) and a third heating coil (60F). The heating coils (60D, 60E, 60F) are wrapped spirally around the mounting cylinder (50) in a clockwise direction. The first heating coil (60D) has two contacts (D1, D2). The second heating coil (60E) has two contacts (E1, E2). The third heating coil (60F) has two contacts (F1, F2).

When the switch (20) is adjusted to make the heating coils (60D, 60E, 60F) generate a maximum heat, the second and third heating coils (60E, 60F) connect to each other in series and then connect to the first heating coil (60D) in parallel. The contacts (E2, F1) connect to each other. A first current flows into the contact (D1) and flows out of the contact (D2). A second current opposite to the first current flows into the contact (F2) and flows out of the contact (E1), as shown in FIG. 5. A magnetic force from the electrified first heating coil (60D) opposes and cancels out a magnetic force from the electrified second and third coils (60E, 60F) and therefore the electromagnetic radiation of the hair dryer is reduced.

When the switch (20) is adjusted to make the heating coils (60D, 60E, 60F) generate an average heat, the first heating coil (60D) is not electrified. The second and third heating coils (60E, 60F) connect to each other in series. The contacts (E2, F2) connect to each other. A current flows into the contact (E1) and flows out of the contact (E2). The current on the second heating coil (60E) from the outside end to the inside end of the mounting cylinder (50) is opposite to the current on the third heating coil (60F) from the inside end to the outside end, as shown in FIG. 6. Therefore, the second and third electrified heating coils (60E, 60F) generate opposite magnetic forces canceling out each other to reduce the electromagnetic radiation of the hair dryer.

When the switch (20) is adjusted to make the heating coils (60D, 60E, 60F) generate a minimum heat, the heating coils (60D, 60E, 60F) connect to each other in series. The contacts (D2, F2) connect to each other. The contacts (E2, F1) connect to each other. A current flows into the contact (D1) and flows out of the contact (E1). The current on the first heating coil (60D) from the outside end to the inside end of the mounting cylinder (50) is opposite to the current on the second and third heating coils (60E, 60F) from the inside end to the outside end, as shown in FIG. 7. Therefore, a magnetic force from the first heating coil (60D) opposes and cancels out a magnetic force from the second and third heating coils (60E, 60F) to reduce the electromagnetic radiation of the hair dryer.

With reference to FIG. 8, a third embodiment of a hair dryer in accordance with the present invention has a first heating coil (60G) and a second heating coil (60H) and connecting to each other in series. Each of the heating coils (60G, 60H) has two contacts, a first coil segment (61) and a second coil segment (62). The first coil segment (61) is wrapped spirally around the mounting cylinder (50) in a clockwise direction. The second coil segment (62) is formed integrally on the first coil segment (61) and is wrapped spirally around the mounting cylinder (50) in a counterclockwise direction. When the heating coils (60G, 60H) is electrified with a current flowing in a single direction along the axis of the mounting cylinder (50), the first and second coils (61, 62) of each heating coil (60G, 60H) generate two opposite magnetic forces canceling out each other. Therefore, the electromagnetic radiation of the hair dryer is reduced.

The arrangement of the heating coils (60A, 60B, 60C, 60D, 60E, 60F, 60G, 60H) cooperating with the currents on each heating coils in particular directions generates opposite magnetic forces canceling out each other to efficiently reduce the harmful electromagnetic radiation of the hair dryer. Furthermore, the heating coils (60A, 60B, 60C, 60D, 60E, 60F, 60G, 60H) arranged abreast without any overlapping or interleaved parts do not cause a short circuit to break the hair dryer. Therefore, hair dryer is safe for use.

Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A hair dryer comprising: a casing being hollow and having a barrel formed on the casing and having a passage defined in the barrel, a cavity defined in the casing and communicating with the passage, at least one air inlet and an air outlet defined in the casing and communicating with the cavity; a switch mounted on the casing; a blower mounted in the cavity in the casing and having a motor mounted in the cavity and connecting to the switch and a fan connected rotatably to the motor; and a mounting cylinder being heat-resistant and insulating and mounted in the passage; and multiple heating coils wrapped spirally around the mounting cylinder, arranged abreast and kept free from overlapping and interleaved parts and connecting to the switch, at least one of the heating coils wrapped in a clockwise direction and at least one of the heating coils wrapped in a counterclockwise direction; whereby the heating coils are electrified and currents on the heating coils are in a same direction to generate opposite magnetic forces canceling out each other.
 2. A hair dryer comprising: a casing being hollow and having a barrel formed on the casing and having a passage defined in the barrel, a cavity defined in the casing and communicating with the passage, at least one air inlet and an air outlet defined in the casing and communicating with the cavity; a switch mounted on the casing; a blower mounted in the cavity in the casing and having a motor mounted in the cavity and connecting to the switch and a fan blade mounted pivotally on the motor; and a mounting cylinder mounted in the passage; and multiple heating coils wrapped spirally around the mounting cylinder in a clockwise direction, arranged abreast and kept free from overlapping and interleaved parts and connecting to the switch; whereby the heating coils are electrified and a current on at least one of the heating coils is in a first direction and currents on remains of the heating coils is in a second direction opposite to the first direction to generate opposite magnetic forces canceling out each other.
 3. A hair dryer comprising: a casing being hollow and having a barrel formed on the casing and having a passage defined in the barrel, a cavity defined in the casing and communicating with the passage, at least one air inlet and an air outlet defined in the casing and communicating with the cavity; a switch mounted on the casing; a blower mounted in the cavity in the casing and having a motor mounted in the cavity and connecting to the switch and a fan blade mounted pivotally on the motor; and a mounting cylinder mounted in the passage; and multiple heating coils wrapped spirally around the mounting cylinder, arranged abreast and kept free from overlapping and interleaved parts, connecting to the switch and each heating coil having a first coil segment wrapped in a clockwise direction and a second coil segment formed integrally with the first coil segment and wrapped in a counterclockwise direction; whereby the heating coils are electrified and the first and second coil segments of each heating coil generate opposite magnetic forces canceling out each other. 